Not applicable
1. The Field of the Invention
The present invention relates generally to vehicle transmissions. More particularly, it concerns a variable-ratio transmission device.
2. Description of Related Art
Transmission devices are well known in the field of motorized vehicles for converting and transmitting the force generated by an engine to an output shaft. It is known to make efficient use of the motor power by adjusting the gear ratio between the input and output shafts responsive to variation in loads on the output shaft, or on the input shaft. For example, a higher gear ratio often provides a more efficient transfer of force for larger loads on the output shaft. Conversely, a lower gear ratio often suffices for lesser loads on the output shaft.
The need to optimize the motor power by varying the gear ratio has motivated the development of many different transmission devices capable of shifting between gear ratios. The standard transmission is known in the field to permit an operator to shift between various gear ratios by operating a hand-shift lever in conjunction with a foot clutch. Automatic transmissions have been developed which accomplish an automatic shifting between gear ratios responsive to increases and decreases in load on the output shaft.
Another approach to vehicle transmissions is the concept of a continuously variable transmission, which automakers have attempted for years to develop. It is thought that energy transfer between the motor and the output shaft can be further optimized by providing an infinite range of gear ratios between the minimum and maximum gear ratios, instead of merely four or five different gear ratios. This idea is a good one, since variation in load on the output shaft tends to increase and decrease gradually and continuously. Indeed, it stands to reason that provision of an optimal gear ratio for each and every load variation on the output shaft would maximize the efficiency of the vehicle. However, there have been many practical difficulties with the prior art transmission devices which offer continuously variable gear ratios.
There is thus a need for a variable-ratio transmission which is simple in design, manufacture and operation.
The prior art is thus characterized by several disadvantages that are addressed by the present invention. The present invention minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.
It is therefore an object of the present invention to provide a variable-ratio transmission which is simple in design and operation.
It is another object of the invention, in accordance with one aspect thereof, to provide such a transmission capable of converting rotational motion to reciprocating, linear motion at variable ratios.
It is a further object of the invention, in accordance with one aspect thereof, to provide such a transmission capable of varying a ratio of movement between gear members during movement of said gear members.
The above objects and others not specifically recited are realized in a specific illustrative embodiment of a variable-ratio transmission device. A first translational member is pivotally intercoupled to a first rotational member by at least one connecting arm. The output member could be a gear, a piston, or any other suitable output member. The connecting arm has a first portion pivotally connected to the first translational member at a first pivot point, and a second portion pivotally and adjustably connected to the first rotational member at a first radial attachment point removed from the center of rotation of the first rotational member. The first radial attachment point and the center of rotation thereby define a first attachment radius. The location of the first radial attachment point with respect to the first rotational member is variable to thereby increase and decrease the first attachment radius, which in turn modifies a ratio of movement between the first rotational member and the first translational member.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention without undue experimentation. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.